Mirror brake mechanism of an SLR camera

ABSTRACT

A mirror brake mechanism of an SLR camera for applying a brake to a mirror pivoted about a mirror rotational shaft to be swingable between a viewing position and a retracted position. The mirror brake mechanism includes a brake shaft which is independent of the mirror rotational shaft and positionally aligned along an extension line of the mirror rotational shaft; an interlocking rotating member disposed on one of laterally opposite sides of the mirror and rotatable about the brake shaft; a mirror drive shaft which connects a mirror seat, on which the mirror is mounted, and the interlocking rotating member to each other in a rotational direction about the mirror drive shaft; a brake drum which rotates in association with the interlocking rotating member; and a mirror brake member which is brought into contact with and disengaged from the brake drum.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mirror brake mechanism of an SLRcamera equipped with a quick-return mirror that swings between a viewingposition and a retracted position.

2. Description of the Related Art

The quick-return mirror (hereinafter referred to simply as a mirror) ofan SLR camera swings between a viewing position, in which lighttraveling from a photographing lens is incident on the quick-returnmirror and reflected thereby toward a viewfinder optical system, and aretracted position, in which the light traveling from the photographinglens is allowed to be incident on film or an image pickup device such asan image sensor without being reflected by the mirror. In 35 mm-formatSLR compact cameras, it is typically the case that the mirror is simplymade to bump against a mirror-up stopper to stop thereat when the mirrorswings up from the viewing position to the retracted position; however,in medium format SLR cameras, the shock produced upon the mirror beingretracted to the retracted position from the viewing position is greatbecause the inertia of the mirror is great. Accordingly, a medium formatSLR camera equipped with a mirror-up brake mechanism to reduce such ashock is known in the art, e.g., Japanese Unexamined Patent PublicationNo. S57-70524.

In the mirror brake mechanism disclosed in Japanese Unexamined PatentPublication No. S57-70524, a sector gear is integrally formed with amirror seat (which holds the mirror) to extend toward the rear of therotational shaft of the mirror seat, and a brake mechanism is installedin association with the sector gear. Due to this structure, aninstallation space for the mirror brake mechanism is required behind themirror (mirror box), which is disadvantageous in regard tominiaturization of the camera.

SUMMARY OF THE INVENTION

The present invention has been devised based on an awareness of theabove described issues in the mirror brake mechanism of conventionalmedium format SLR cameras and provides a mirror brake mechanism of anSLR camera which is configured to make it possible to reduce thethickness (length) of the camera.

In conventional mirror brake mechanisms of SLR cameras, since a sectorgear is formed integral with a mirror seat to extend toward the rear ofthe rotational shaft of the mirror seat and since a mirror brakemechanism is installed in association with the sector gear, aninstallation space for the mirror brake mechanism is inevitably requiredbehind the mirror box. By resolving this issue, the present inventionhas been accomplished from the viewpoint that, if an interlockingrotating member which rotates with the mirror seat and is positionedcoaxially with the axis of rotation of the mirror seat is installed onone of laterally opposite sides of the mirror and if the interlockingrotating member is made to operate in association with the mirror brakemechanism, a degree of freedom is given to the placement of the mirrorbrake mechanism to thereby make it possible to reduce the thickness(length) of the camera.

According to an aspect of the present invention, a mirror brakemechanism of an SLR camera is provided for applying a brake to a mirrorpivoted about a mirror rotational shaft to be swingable between aviewing position, in which light traveling from a photographing opticalsystem is incident on the mirror and reflected thereby toward aviewfinder optical system, and a retracted position, in which the lighttraveling from the photographing optical system is allowed to beincident on an image sensor without being reflected by the mirror. Themirror brake mechanism includes a brake shaft which is independent ofthe mirror rotational shaft and positionally aligned along an extensionline of the mirror rotational shaft; an interlocking rotating memberdisposed on one of laterally opposite sides of the mirror and rotatableabout the brake shaft; a mirror drive shaft which connects a mirrorseat, on which the mirror is mounted, and the interlocking rotatingmember to each other in a rotational direction about the mirror driveshaft; a brake drum which rotates in association with the interlockingrotating member; and a mirror brake member which is brought into contactwith and disengaged from the brake drum.

It is desirable for the interlocking rotating member, the brake drum andthe mirror brake member to be disposed on the one of the laterallyopposite sides of the mirror.

If the interlocking rotating member includes an elongated hole elongatedin a radial direction of the interlocking rotating member, wherein themirror drive shaft is connected to a lateral side of the mirror seat andis inserted into the elongated hole of the interlocking rotating member,a deviation in coaxial alignment between the shaft (brake shaft) of theinterlocking rotating member and the mirror rotational shaft of themirror can be absorbed.

It is desirable for the interlocking rotating member to include a sectorgear, and for the mirror control mechanism to include a speed-up geartrain that is disposed between the sector gear and the brake drum.

It is desirable for the mirror brake member to include a brake leverthat is swingable between a brake applying position in which a brakeshoe fixed to one end of the brake lever is pressed against the brakedrum to brake the brake drum and a brake release position in which thebrake shoe is disengaged from the brake drum, and for the mirror brakemechanism to include a brake spring which biases the brake lever towardthe brake applying position.

It is desirable for the mirror brake mechanism to include a mirror driveunit which swings the mirror via the mirror drive shaft.

It is desirable for the mirror drive unit to include an operativelyassociated mechanism which operates in association with the mirror driveunit to prevent the mirror brake member from applying a brake to thebrake drum when the mirror is in the viewing position, to brake thebrake drum before the mirror reaches the retracted position when themirror swings from the viewing position to the retracted position, andto release the brake from the brake drum applied via the mirror brakemember before the mirror commences to swing when the mirror swings fromthe retracted position to the viewing position.

It is desirable for axes of the brake shaft, the mirror drive shaft andthe brake drum to be parallel to one another.

According to the present invention, since the interlocking rotatingmember that rotates with the mirror seat and is positioned coaxiallywith the axis of rotation of the mirror seat is installed on one oflaterally opposite sides of the mirror and since the interlockingrotating member is made to operate in association with the brake drumthat serves as an element of the mirror brake mechanism, the depth ofthe installation space for the mirror brake mechanism can be small,which makes miniaturization of the camera body possible.

The present disclosure relates to subject matter contained in JapanesePatent Applications Nos. 2009-294671 (filed on Dec. 25, 2009) and2010-271872 (filed on Dec. 6, 2010), which are expressly incorporatedherein by reference in their entireties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a mirror unit and anembodiment of a mirror brake unit of a mirror brake mechanism accordingto the present invention with a mirror drive unit removed from themirror drive apparatus;

FIG. 2 is a rear perspective view of the mirror brake unit, showing thestructure thereof;

FIG. 3 is a side elevational view of the mirror unit and the mirrorbrake unit;

FIG. 4 is a side elevational view of the mirror drive apparatus, showingthe embodiment of the mirror unit shown in FIGS. 1 and 3 and anembodiment of the mirror drive unit in a mirror-down position with themirror brake unit removed from the mirror drive apparatus;

FIG. 5 is a side elevational view of the mirror unit and the mirrordrive unit shown in FIG. 4 in a mirror-up state;

FIG. 6 is a side elevational view of the mirror drive apparatus in amirror-down position;

FIG. 7 is a side elevational view of the mirror drive apparatus, showinga mirror brake commencement position during an upward movement of thequick return mirror;

FIG. 8 is a side elevational view of the mirror drive apparatus, showinga state thereof in the mirror-up position;

FIG. 9 is a side elevational view of the mirror drive apparatus, showinga state thereof in a mirror brake release position;

FIG. 10 is aside elevational view of the mirror drive apparatus, showinga state thereof during a downward movement of the quick-return mirror(during charging of a mirror drive spring);

FIG. 11 is an exploded perspective view of the mirror drive unit,showing a manner of supporting a mirror control cam and a brake releaselever of the mirror drive unit;

FIG. 12 is a timing chart showing the timings of the mirror up/downoperation of the quick-return mirror and the brake ON/OFF operation thatare performed by operations of the brake release lever in associationwith the angle of rotation of the mirror control cam of the mirror driveunit of the mirror drive apparatus;

FIG. 13 is a timing chart showing the timings of the mirror up/downoperation of the quick-return mirror and the brake ON/OFF operation inassociation with the angle of rotation of a mirror drive lever of themirror drive unit; and

FIG. 14 is a front elevational view of the mirror control cam, showingthe shape thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The illustrated embodiment of the mirror drive apparatus that isincorporated in a digital SLR camera is provided with a mirror unit 100,a mirror brake unit (mirror brake mechanism) 200 and a mirror drive unit(mirror drive mechanism) 300 which are constructed independently of oneanother. FIGS. 1 and 3 each show the mirror unit 100 and the mirrorbrake unit 200, FIG. 2 shows the mirror brake unit 200, FIGS. 4 and 5each show part of the mirror unit 100 and the mirror drive unit 300 withthe mirror brake unit 200 removed from the mirror drive apparatus, andFIGS. 6 through 10 show an assembled state of the whole mirror driveapparatus. Although the mirror brake unit 200 is provided with a brakemount plate 201, the brake mount plate 201 is not shown in FIGS. 6through 10 for the sake of clarity. In the following descriptions, thecomponents of the mirror unit 100 are designated by reference numeralsin their hundreds, the components of the mirror brake unit 200 aredesignated by reference numerals in their two hundreds, and thecomponents of the mirror drive unit 300 are designated by referencenumerals in their three hundreds.

[Mirror Unit 100]

The mirror unit 100 is provided with a mirror (quick-return mirror) 101and a mirror seat 111 in the shape of a substantially rectangular frameto which the mirror 101 is fixedly mounted. A mirror rotational shaft112 is fixed to the mirror seat 111 so that both ends of the mirrorrotational shaft 112 project in opposite directions away from each otherfrom opposite sides of the mirror seat 111 at one end of the mirror seat111. Two mirror shaft bearings 113 are rotatably fitted on both ends ofthe mirror rotational shaft 112, respectively. The mirror seat 111 isinstalled in a mirror box (not shown) via the mirror rotational shaft112 and the mirror shaft bearings 113. In a state where this mirror boxis mounted inside a camera body (not shown), the mirror 101 is pivotedabout the mirror rotational shaft 112 to be swingable between a viewingposition (shown in FIG. 3) at which object light traveling from aphotographing optical system OS is incident on the mirror 101 andreflected thereby toward a viewfinder optical system (not shown) and aretracted position (photographing position) at which the light travelingfrom the photographing optical system OS is allowed to be incident on animage pickup device (image sensor) (not shown).

The mirror seat 111 is provided on one side thereof with a bearing(mirror drive shaft bearing) 114 which is positioned toward the free endof the mirror sheet 111 with respect to the mirror rotational shaft 112.A mirror drive shaft 400 is fitted in the bearing 114. The mirror driveshaft 400 is an element which connects the mirror seat 111 to each ofthe mirror brake unit 200 (a sector gear 211 thereof) and the mirrordrive unit 300 (a mirror drive lever 311 thereof; see FIG. 4 and thefollowing drawings). The mirror drive shaft 400 is provided with a D-cutcross-sectional portion 400D (see FIG. 2) which is inserted into thebearing 114 of the mirror seat 111. The mirror drive shaft 400 is fixedto the mirror seat 111 by a set screw (not shown) which is screwed intothe bearing 114 in a radial direction thereof until the set screwcontacts the flattened portion of the D-cut cross-sectional portion400D.

[Mirror Brake Unit 200]

The mirror brake unit 200 is a mirror brake mechanism which applies abrake to the swing motion of the mirror seat 111, to which the mirror101 is mounted. The elements of the mirror brake unit 200 are mounted toa brake mount plate 201 that is provided as a separate member from theaforementioned mirror box that supports the mirror shaft bearing 113 ofthe mirror seat 111.

The mirror brake unit 200 is provided with the sector gear (interlockingrotating member) 211 that is pivoted on the brake mount plate 201 via abrake shaft 212. The brake shaft 212 is positioned independently on anextension line of the axis of the mirror rotational shaft 112 in a statewhere the mirror unit 100 is combined with the mirror brake unit 200.The sector gear 211 is disposed so that the geared portion thereof ispositioned further forward (toward the photographing optical system OS)than the brake shaft 212. An elongated hole 213 that is elongated in aradial direction of the sector gear 211 is formed on the sector gear 211at a position a predetermined distance away from the brake shaft 212.The mirror drive shaft 400 of the mirror unit 100 is inserted into theelongated hole 213. The mirror seat 111 and the sector gear 211 arecoupled (connected) to each other via the mirror drive shaft 400 in therotational direction of the mirror seat 111 and the sector gear 211. Thewidth of the elongated hole 213 is determined so as to remove play inthe widthwise (minor axis) direction thereof between the elongated hole213 and the mirror drive shaft 400. In addition, the distance betweenthe center of the elongated hole 213 in the lengthwise direction thereofand the brake shaft 212 is determined to be substantially identical tothe distance between the mirror rotational shaft 112 and the mirrordrive shaft 400. By forming the elongated hole 213, in which the mirrordrive shaft 400 is inserted, as a hole elongated in a radial directionof the sector gear 211 in the above described manner, a deviation incoaxial alignment between the mirror rotational shaft 112 and the brakeshaft 212 can be absorbed.

The mirror brake unit 200 is provided with a speed-up gear (speed-upgear train) 221 and a brake drum 231, each of which is mounted to thebrake mount plate 201. The sector gear 211 is in mesh with the brakedrum 231 via the speed-up gear 221. More specifically, the speed-up gear221 is provided with a small gear 223 and a large gear 224 which areformed integrally and coaxially with a shaft 222 that is rotatablysupported by the brake mount plate 201. The small gear 223 and the largegear 224 are in mesh with the sector gear 211 and a small gear 233 (seeFIG. 3) of the brake drum 231, respectively. The speed-up gear 221 andthe brake drum 231 are rotatably supported by the brake mount plate 201via the shaft 222 and a drum shaft 232, respectively. In addition, thespeed-up gear 221 and the brake drum 231 are prevented from coming offthe shaft 222 and the drum shaft 232, respectively, by a retaining plate251 which is fixed at one end thereof to the brake mount plate 201. Thesmall gear 223 and the large gear 224 of the speed-up gear 221, and thebrake drum 231 that includes the small gear 233, which are arranged onthe brake mount plate 201 and driven to rotate by the sector gear 211,are all positioned in front of the brake shaft 212. Specifically, inmedium format SLR cameras, miniaturization (reduction in thickness) ofthe whole camera becomes possible by the above described arrangement inwhich the small gear 223, the large gear 224 and the brake drum 231 thatincludes the small gear 233 are all positioned in front of the brakeshaft 212, i.e., on one side of the mirror box, since the mirror of amedium format SLR camera is generally large in size.

The mirror brake unit 200 is provided with a brake lever (mirror brakemember) 241 which is pivoted about a brake lever shaft 242 fixed to thebrake mount plate 201 so that the brake lever 241 can freely rotateabout the brake lever shaft 242. The brake lever 241 is for applying abrake to the brake drum 231 while in motion. A brake shoe 243, which isbrought into contact with the outer peripheral surface of the brake drum231, is fixed to an end of the brake lever 241. Forward and reverseswing movements of the brake lever 241 about the brake lever shaft 242cause the brake shoe 243 to correspondingly move toward and away fromthe brake drum 231. The brake drum 231 can be formed from, e.g., brass,and the brake shoe 243 can be formed from, e.g., POM (polyoxymethylene).

The brake lever 241 is biased to rotate in a direction to press thebrake shoe 243 against the outer peripheral surface of the brake drum231 by a brake spring (extension spring/biaser) 244. The brake lever 241is provided, on the opposite side of the brake lever shaft 242 withrespect to the brake shoe 243, with a brake release projection 245, andis further provided in the vicinity of the brake shoe 243 with a brakecontrol recess (brake commencement timing setter) 246 for controllingthe timing of the commencement of application of the brake (brake shoe243) to the brake drum 231. The brake release projection 245 and thebrake control recess 246 are engageable with a brake release lever 361and a mirror-drive-spring charge lever 321 of the mirror drive unit 300in order to control the position of the brake lever 241.

[Mirror Drive Unit 300]

The mirror drive unit 300 is positioned between the mirror unit 100 andthe mirror brake unit 200 in a state where the mirror drive apparatus(100, 200 and 300) is installed in the camera body (not shown). As shownin FIGS. 4 and 5, the mirror drive unit 300 is provided with a sideplate 301 which forms the right side wall of the mirror box as viewedfrom the front, and each component of the mirror drive unit 300 otherthan the side plate 301 is mounted to an outer side of the side plate301.

The mirror drive lever 311 and the mirror-drive-spring charge lever 321are pivoted about a lever pivot shaft 312 that is fixed to the sideplate 301 to be coaxially rotatable relative to each other, and a camgear 331 on which a mirror control cam 333 is integrally formed issupported by a cam gear shaft 332 to be freely rotatable thereon. Thecam gear shaft 332 is fixed to the side plate 301. The mirror driveshaft 400 of the mirror unit 100 is engaged in an elongated hole 313which is formed at one end (right end with respect to FIG. 5) of themirror drive lever 311. A swing motion of the mirror drive lever 311about the lever pivot shaft 312 between a mirror-down position and amirror-up position causes the mirror seat 111 to move between theviewing position and the retracted position.

The mirror-drive-spring charge lever 321 and the mirror drive lever 311are connected to each other via a connecting spring (torsion spring) 323and rotate together at normal times. Specifically, as shown in FIGS. 4and 5, a coiled portion 323C of the connecting spring 323 is fitted onthe lever pivot shaft 312, and two arms 323A and 323B formed at bothends of the of the connecting spring 323 are positioned between a springhook portion 321B of the mirror-drive-spring charge lever 321 and aspring hook portion 311B of the mirror drive lever 311 to be hookedthereon, respectively, so that the mirror-drive-spring charge lever 321and the mirror drive lever 311 are biased to rotate by the connectingspring 323 in directions to make an engaging piece 324 which is formedon the mirror-drive-spring charge lever 321 and a contacting portion 311a which is formed on the mirror drive lever 311 engage with each other.In a state where one of the mirror-drive-spring charge lever 321 and themirror drive lever 311 is prevented from rotating, a rotation of theother of the mirror-drive-spring charge lever 321 and the mirror drivelever 311 in a direction to make the engaging piece 324 and thecontacting portion 311 a move away from each other causes the connectingspring 323 to be overcharged.

The mirror drive unit 300 is provided, on a collared portion of themirror-drive-spring charge lever 321 which is formed by bending part ofthe mirror-drive-spring charge lever 321 in a direction orthogonal to aplane in which the mirror-drive-spring charge lever 321 rotates, with anadjustment washer (adjustment spacer/shim/brake commencement timingsetter) 325 which is fixed to the collared portion by a set screw. In astate where the mirror brake unit 200 and the mirror drive unit 300 arecombined, the adjustment washer 325 acts as an engaging portion whichprevents the brake lever 241 from rotating in a brake-actuatingdirection by engaging with the brake control recess 246 of the brakelever 241 that is biased to rotate by the brake spring 244 (see FIGS. 6and 7). The adjustment washer 325 consists of one or more washers, canbe adjusted in thickness by changing a combination of washers havingdifferent thicknesses, and constitutes a brake timing adjuster foradjusting the timing of contact of the brake shoe 243 of the brake lever241 with the brake drum 231.

One end of the mirror drive spring 326 is engaged with themirror-drive-spring charge lever 321 at an end thereof on the oppositeside of the lever pivot shaft 312 with respect to the engaging piece324. The other end of the mirror drive spring 326 is engaged with theside plate 301 to continuously bias the mirror-drive-spring charge lever321 to rotate in the mirror-up direction. In addition, a cam roller 327is supported on the mirror-drive-spring charge lever 321 at an endthereof on the opposite side of the lever pivot shaft 312 with respectto the engaging piece 324 to be freely rotatable on the axis of the camroller 327. The cam roller 327 limits the rotation of themirror-drive-spring charge lever 321 by engaging with a peripheral camsurface 333 a of the mirror control cam 333 to control the charging andreleasing of the mirror drive spring 326.

The mirror control cam 333 that is made from a plate cam is asingle-rotation cam which performs a sequence of operations (mirrorup/down cycle) by rotating by a single rotation (360 degree rotation)via the cam roller 327, which rolls on the peripheral cam surface 333 a,and the mirror-drive-spring charge lever 321, which rotatably supportsthe cam roller 327. In the present embodiment, the peripheral camsurface 333 a is formed in the shape of a cycloid about the cam gearshaft 332, and a single rotation of the peripheral cam surface 333 acauses the charged mirror drive spring 326 to be released, the mirror101 to move up to the retracted position, the mirror 101 to be held inthe retracted position, the mirror drive spring 326 to be charged, themirror 101 to move down to the viewing position, and the mirror 101 tobe held in the viewing position. FIG. 14 shows the shape (contour) ofthe peripheral cam surface 333 a of the mirror control cam 333. Theperipheral cam surface 333 a includes a viewing position (mirror-downposition) holding section X that is formed as a concentric arc section(maximum radius section) centered about and concentric with the cam gearshaft 332. Next to the viewing position holding section X, theperipheral cam surface 333 a includes acharge-release/mirror-up/mirror-up-position-holding section (smalldiameter portion/minimum radius section) Y and a charge/mirror-downsection (charging section) Z in that order in the rotation direction ofthe mirror control cam 333. The mirror control cam 333 is provided inthe viewing position (mirror-down position) holding section X with arotation reference position (zero degree position; see FIG. 12). Thiszero degree position designates a position to stop the mirror controlcam 333 at a charging position at which the mirror drive spring 326completes charging (being fully extended) by the mirror-drive-springcharge lever 321. To allow this rotation reference position to bevisible during assembly, the mirror control cam 333 is provided on aside thereof with a rotation position reference index 333 b (whichappears in FIG. 11 also) representing the rotation reference position.The operation of the mirror control cam 333 is controlled so that thecam roller 327 stops at the zero degree position. A roller holdingrecess 333 c (shown by a two-dot chain line in FIG. 14) which allows thecam roller 327 to be engaged therein to hold the mirror-drive-springcharge lever 321 at the charging position is formed on the peripheralcam surface 333 a to correspond to the zero degree position (therotation position reference index 333 b). The mirror-drive-spring chargelever 321 constitutes a brake lever control mechanism which brings thebrake shoe 243 of the brake lever 241 to be pressed against anddisengaged from the brake drum 231 by a single rotation of the mirrorcontrol cam 333.

A mirror motor MM is connected to the cam gear 331 via a reduction geartrain 341 and a pinion 343 fixed to the rotational shaft of the mirrormotor MM. Rotation of the rotational shaft of the mirror motor MM istransmitted from the pinion 343 to the cam gear 331 via the reductiongear train 341. The mirror drive unit 300 is provided with a code brush351 which is mounted on the side of the cam gear 331 which faces theside plate 301. The mirror drive unit 300 is further provided with acode plate 352 having a land (land pattern) which is fixed to the sideplate 301. The land of the code plate 352 is formed along the path ofthe code brush 351, so that the code brush 351 slides on the code plate352 when the cam gear 331 rotates relative to the side plate 301.Rotational positions (the mirror-up position and the mirror-downposition) of the cam gear 331 are detected via a combination of the codebrush 351 and the code plate 352. The code plate 352 and the mirrormotor MM are connected to a control circuit 401 (see FIGS. 4 and 5). Thecontrol circuit 401 controls the operation of the mirror motor MM inaccordance with the position of the mirror control cam 333 which isdetected via the code plate 352 and the code brush 351.

The mirror drive unit 300 is provided, between the side plate 301 and asupplemental plate 301H (see FIG. 11) parallel to the side plate 301,with the aforementioned brake release lever 361 which is pivoted about apivot 362 that is fixedly supported onto the inner side of thesupplemental plate 301H to be disposed between the side plate 301 andthe supplemental plate 301H. The brake release lever 361 is not shown inFIGS. 4 and 5 though the brake release lever 361 is an element of themirror drive unit 300. The brake release lever 361 is provided with abrake release arm 363 that is engageable with the brake releaseprojection 245 of the mirror brake unit 200. The brake release lever 361is further provided, on the opposite side of the pivot 362 with respectto the brake release arm 363 with a cam portion (cam surface) 364 (seeFIGS. 6 through 11) which extends in a plane orthogonal to the axis ofrotation (the cam gear shaft 332) of the mirror control cam 333. Themirror control cam 333 is provided, at a position eccentric from theaxis of the cam gear shaft 332, with a brake release pin 334 whichprojects in a direction parallel to the axis of rotation (the cam gearshaft 332) of the mirror control cam 333. The mirror control cam 333rotates the brake release lever 361 in a brake releasing direction viaengagement of the brake release pin 334 with the cam portion 364 againstthe biasing force of the brake spring 244.

The mirror unit 100, the mirror brake unit 200 and the mirror drive unit300 are constructed independently of one another in advance and areinstalled in the camera body (not shown) upon assembly. The mirror brakeunit 200 is normally mounted to the mirror unit 100 after the mirrordrive unit 300 is mounted to the mirror unit 100. The mirror brake unit200 is disposed at a position where the axis of the mirror rotationalshaft 112 is aligned with the axis of the brake shaft 212 of the sectorgear 211. The mirror drive shaft 400 is engaged in the elongated hole213 of the sector gear 211 through the elongated hole 313 of the mirrordrive lever 311, and the mirror unit 100, the mirror brake unit 200 andthe mirror drive unit 300 are linked with one another via the mirrordrive shaft 400. In addition, the brake lever shaft 242 is positionedcoaxially with the lever pivot shaft 312, the brake release arm 363 andthe cam portion 364 of the brake release lever 361 face the brakerelease projection 245 of the brake lever 241 and the brake release pin334 of the mirror control cam 333, respectively, and the adjustmentwasher 325 of the mirror-drive-spring charge lever 321 is engaged withthe brake control recess 246 of the brake lever 241 (see FIGS. 6 through10).

Operations of the mirror drive apparatus in an assembled state will behereinafter discussed with reference to FIGS. 6 through 10, 12 and 13.FIG. 12 is a timing chart showing the timings of the mirror up/downoperation of the mirror 101 and the brake ON/OFF operation(contacting/separating operation of the brake lever 241 relative to thebrake drum 231) that are performed in association with the angle ofrotation of the mirror control cam 333 and the operation of the brakerelease lever 361. FIG. 13 is a timing chart showing the timings of themirror up/down operation of the mirror 101 and the brake ON/OFFoperation in association with the angle of rotation of the mirror drivelever 311. In the timing charts of FIGS. 12 and 13, the mirror controlcam 333 at a zero degree angle and the mirror drive lever 311 at a zerodegree angle designate the initial positions thereof in which the mirror101 is held in the viewing position (mirror-down position). The mirrorcontrol cam 333 only rotates one way, rotating through 360 degrees fromthe initial position of a zero degree angle to the initial position of azero degree angle; however, the mirror drive lever 311 swings oncebetween the zero degree position and an approximately 20 degree positionwhile the mirror control cam 333 rotates by a single rotation from thezero degree position to the 360 degree position.

When the mirror 101 is held at the viewing position, the cam roller 327is positioned in the charge completion range (the viewing positionholding section X) of the mirror control cam 333 as shown in FIG. 6, themirror-drive-spring charge lever 321 is held at the charging position,in which the mirror drive spring 326 is charged (fully extended), andthe mirror drive lever 311 is held at the mirror-down position. At thisstage, the mirror seat 111 is prevented from further rotating from theviewing position, at which the mirror seat 111 comes in contact with amirror-down stopper (not shown), so that the mirror drive lever 311 isprevented from rotating in the mirror-down direction; however, themirror-drive-spring charge lever 321 further rotates in the mirror-downdirection by the peripheral cam surface 333 a so that the engaging piece324 moves away from the contacting portion 311 a to thereby create aclearances (see FIGS. 4 and 6). Accordingly, the connecting spring 323moves into an overcharged state. Additionally, the adjustment washer 325of the mirror-drive-spring charge lever 321 holds the brake shoe 243 ina position (the brake releasing position) spaced away from the brakedrum 231 via engaging in the brake control recess 246. When the mirrorseat 111 is in contact with the mirror-down stopper, the cam roller 327of the mirror-drive-spring charge lever 321 is in contact with a viewingposition starting end Z′ (see FIG. 14) of the mirror control cam 333.The viewing position starting end Z′ is a specific position in thecharging section Z in the vicinity of the viewing position holdingsection X, and the overcharging of the connecting spring 323 proceedsfrom this time (position) onwards.

Upon the mirror motor MM being actuated (i.e., upon a shutter release)when the mirror 101 is in the viewing position, the mirror control cam333 rotates clockwise with respect to FIG. 6 together with the cam gear331 that is rotated via the reduction gear train 341. In an initialstage of the rotation of the mirror control cam 333, the cam roller 327drops to the mirror-up-position holding section (charge-releasesection/minimum radius section) Y radially inwards from the chargecompletion range (the viewing position holding section X) of theperipheral cam surface 333 a. Upon the cam roller 327 dropping down tomirror-up-position holding section Y, the constraint of the cam roller327 is instantly released to thereby release the mirror-drive-springcharge lever 321. Thereupon, the mirror-drive-spring charge lever 321rotates toward the mirror-up position (counterclockwise with respect toFIGS. 4 through 10) by the resilient tensile force (resiliency) of themirror drive spring 326. Furthermore, the control circuit 401 detectsvia the code brush 351 and the code plate 352 that a rotation of themirror control cam 333 has caused the cam roller 327 to move out of theviewing position holding section X of the mirror control cam 333. Uponthis detection, the control circuit 401 stops the mirror motor MMinstantaneously.

The rotation of the mirror-drive-spring charge lever 321 toward themirror-up position causes the mirror drive lever 311 to swing with themirror-drive-spring charge lever 321 about the lever pivot shaft 312,thus causing the mirror seat 111 to swing instantaneously toward theretracted position via the mirror drive shaft 400 (section A in FIG. 12and section A in FIG. 13). This movement of the mirror 101 from theviewing position to the retracted position is carried out swiftly by thespring force of the mirror drive spring 326. The actual time (mirror-uptime) it takes for the mirror 101 to move from the viewing position tothe retracted position can be adjusted by adjusting the strength of themirror drive spring 326. However, if the spring force of the mirrordrive spring 326 is excessively large, the shock produced upon themirror 101 being retracted to the retracted position becomescorrespondingly large. Accordingly, the strength of the mirror drivespring 326 is determined in consideration of the retracting speed of themirror 101, the shock that is produced and also the sequence ofoperations of the entire camera system.

Concurrently with this movement of the mirror 101 toward the retractedposition, the sector gear 211 also rotates toward the retracted position(clockwise with respect to FIGS. 6 through 10) since the mirror driveshaft 400 is engaged in the elongated hole 213 of the sector gear 211.This rotation of the sector gear 211 toward the retracted positioncauses the brake drum 231 to rotate at a high speed via the speed-upgear 221.

The rotation of the mirror-drive-spring charge lever 321 toward themirror-up position causes the brake lever 241, which is biased to rotatein a brake applying direction by the resilient biasing force of thebrake spring 244 so that the brake control recess 246 presses theadjustment washer 325, to swing in a brake applying direction followingthe rotation of the mirror drive lever 311. Subsequently, immediatelybefore the completion of the mirror-up operation of the mirror 101, thebrake shoe 243 of the brake lever 241 is applied against the brake drum231 to thereby start braking the brake drum 231, and the adjustmentwasher 325 commences disengagement from the brake control recess 246(see FIG. 7, point B in FIG. 12, point B in FIG. 13). The adjustmentwasher 325 serves as a member for adjusting (setting) the timing of thiscommencement of the application of the brake shoe 243 of the brake lever241 against the brake drum 231. This timing is advanced if the thicknessof the whole adjustment washer 325 is decreased and retarded if thethickness of the whole adjustment washer 325 is increased.

Further rotation of the mirror drive lever 311 toward the mirror-upposition causes the adjustment washer 325 to be disengaged from thebrake control recess 246, so that the action of brake application to thebrake drum 231 continues (see section C in FIG. 12 and section C in FIG.13). Namely, this action of brake application holds down the swingmovement of the sector gear 211 via the speed-up gear 221, thus rapidlyreducing the swing speed of the mirror seat 111 toward the retractedposition via the mirror drive shaft 400. Thereupon, the mirror seat 111slows down and then bumps against the mirror-up stopper 131 to stop atthe retracted position (see FIG. 8, point H in FIG. 12, point H in FIG.13).

In a state where the mirror seat 111 is at rest in the retractedposition and the mirror control cam 333 is at a standstill, themirror-drive-spring charge lever 321 is at rest in the mirror-upposition, at which the cam roller 327 has dropped down into themirror-up position holding section (small radius section/minimum radiussection) Y of the peripheral cam surface 333 a of the mirror control cam333 and is disengaged from the peripheral cam surface 333 a (see FIG.8). Accordingly, the mirror seat 111 remains still in the retractedposition while being pressed against the mirror-up stopper 131 via themirror-drive-spring charge lever 321, which is biased to rotate by theresilient biasing force of the mirror drive spring 326, the mirror drivelever 311 and the mirror drive shaft 400, and while being braked by thebrake drum 231 which is prevented from rotating by the frictional forcecreated between the brake drum 231 and the brake shoe 243 pressedagainst the brake drum 231 by the resilient biasing force of the brakespring 244 (see FIG. 8). In such a state where the mirror 101 is held inthe retracted position, an exposure/photographing process (imagecapturing process) is performed.

The brake release lever 361 releases the braking effect that is appliedto the brake drum 231 by the brake lever 241 at a specific rotationalphase (position) of the mirror control cam 333 regardless of theposition of the mirror-drive-spring charge lever 321 (point E in FIG.12). Upon completion of the exposure/photographing process (imagecapturing process), the control circuit 401 again actuates the mirrormotor MM to rotate the mirror control cam 333 in the clockwisedirection. This clockwise rotation of the mirror control cam 333 causesthe brake release pin 334 to come in slide contact with the cam portion364 to make the brake release lever 361 swing in the brake releasingdirection (counterclockwise direction with respect to FIG. 9).Thereupon, the brake release arm 363 of the brake release lever 361comes into contact with the brake release projection 245 of the brakelever 241 to rotate the brake lever 241 in the brake releasingdirection, so that the brake shoe 243 is disengaged from the brake drum231 to thereby release the braking effect on the mirror 101 (point E inFIG. 12).

Further clockwise rotation of the mirror control cam 333 causes thecharging section Z of the peripheral cam surface 333 a to startcontacting the cam roller 327 (see FIG. 9). Thereafter, furtherclockwise rotation of the mirror control cam 333 causes the cam roller327 to be pressed (moved) in a direction away from the cam gear shaft332 by the peripheral cam surface 333 a of the mirror control cam 333while rolling on the peripheral cam surface 333 a, which causes themirror-drive-spring charge lever 321 to swing in a charge directioncorresponding to the mirror-down direction (clockwise direction withrespect to FIGS. 4 through 10), thus causing the mirror seat 111 toswing toward the viewing position via the mirror drive lever 311 and themirror drive shaft 400 while charging (extending) the mirror drivespring 326.

Further clockwise rotation of the mirror control cam 333 causes thebrake release pin 334 to be disengaged from the cam portion 364 (point Fin FIG. 12); however, by this stage the adjustment washer 325 has movedto a position so as to come in contact with the brake control recess 246of the brake lever 241 (point F in FIG. 12). Accordingly, the brake shoe243 maintains a brake released state in which the brake shoe 243 isdisengaged from the brake drum 231. Namely, the mirror-drive-springcharge lever 321 has already released the brake (as shown by solid linesin FIG. 10) at a position (shown by two-dot chain lines in FIG. 10)where the adjustment washer 325 comes in contact with the brake controlrecess 246 when it is assumed that the brake release lever 361 does notexist. In this manner, by releasing the brake using the brake releaselever 361 independently of the mirror-drive-spring charge lever 321before the mirror-drive-spring charge lever 321 releases the brake, thephenomenon of interfering with motion of the mirror 101 which is readyto start moving downward is prevented from occurring, so that the mirror101 can be made to move down smoothly. Specifically, themirror-drive-spring charge lever 321 makes the mirror 101 move down bymaking the cam roller 327 enter the charging section Z of the mirrorcontrol cam 333; however, at this time if the brake shoe 243 of thebrake lever 241 is in contact with the brake drum 231, the mirror 101cannot move down smoothly and the connecting spring 323 is overcharged,and accordingly, there is a possibility of the mirror 101 moving largelyto thereby produce a shock at the moment that the adjustment washer 325of the mirror-drive-spring charge lever 321 releases the brake bycontacting and pressing the brake control recess 246. In contrast, byreleasing the brake using the brake release lever 361 that is adifferent member from the mirror-drive-spring charge lever 321, thebrake is released with reliability when the mirror 101 moves down, whichmakes a smooth downward movement of the mirror 101 from the retractedposition to the viewing position possible.

Thereafter, the cam roller 327 rolls on the charging section Z of theperipheral cam surface 333 a of the mirror control cam 333, andtherefore, the mirror-drive-spring charge lever 321 further rotates inthe charge direction (i.e., in the mirror-down direction) to make themirror seat 111 swing down toward the viewing position while chargingthe mirror drive spring 326. The mirror seat 111 enters (arrives at) theviewing position (i.e., the cam roller 327 enters (comes in contactwith) the holding section X from the viewing position starting end Z′ ofthe mirror control cam 333; point D in FIG. 12), and when the cam roller327 has reached (advanced to) the zero degree position (point I in FIG.12) within the holding section X, the control circuit 401 detects aposition on the code plate 352 that corresponds to this zero degreeposition and commands (controls) the mirror control cam 333 (mirrormotor MM) to stop.

The sector gear 211, the speed-up gear 221 and the brake drum 231, whichhave been described above, also function as a speed control mechanism(speed governor) during the time the mirror seat 111 swings between theretracted position and the viewing position (i.e., swings up and down).

The brake lever 241, the mirror-drive-spring charge lever 321 and theadjustment washer 325 constitute a linking mechanism which makes themirror brake unit 200 brake the mirror 101 before the mirror 101 reachesthe retracted position in the course of the retracting movement of themirror 101 toward the retracted position from the viewing position.

The brake release lever 361 and the brake release pin 334 alsoconstitute an operatively associated (detachably connectable) mechanismwhich determines the timing of releasing the brake shoe 243, which isapplied to the mirror 101 by the mirror brake unit 200, upon or beforethe commencement of a swing movement of the mirror 101 toward theviewing position from the retracted position in association withrotation of the mirror control cam 333.

As described above, according to the mirror brake mechanism of an SLRcamera according to the present invention, since the mirror brake unit(mirror brake mechanism) 200 is disposed on one of laterally oppositesides of the mirror 101 so that the brake shaft 212 is positionallyaligned on an extension line of the axis of the mirror rotational shaft112, and since the small gear 223, the large gear 224 of the speed-upgear 221, and the brake drum 231 that includes the small gear 233, whichare driven to rotate by the sector gear 211, are all positioned in frontof the brake shaft 212, the depth of the installation space for themirror brake unit 200 can be small, which makes miniaturization of thecamera body possible.

Additionally, the mirror brake mechanism of an SLR camera according tothe present invention is structured so that the brake shaft 212 of themirror brake unit 200, which operates to brake upward movement of themirror seat 111, is provided as a separate member from the mirrorrotational shaft 112 and so that the mirror brake unit 200 is installedto make the axis of one of the brake shaft 212 and the mirror rotationalshaft 112 substantially coincide with an extension line of the axis ofthe other, the mirror brake unit 200 can be mounted to the mirror unit100 in an easy manner because it is not required to bring one gear intoengagement with another gear when the mirror brake unit 200 is mountedto the mirror unit 100. Moreover, as compared even with the case whereone gear needs to be engaged with another gear when the mirror brakeunit 200 is installed in a camera body, tolerances in dimensional errorof elements/parts and assembly error are increased, facilitatingassembly of the mirror brake mechanism. Furthermore, since all theelements of the mirror brake unit 200 are mounted to the single brakemount plate 201 as a unit, the mirror brake unit 200 itself is easy toassemble and it is also easy to install the mirror brake unit 200 in acamera body.

Although the present invention has been described based on the aboveillustrated embodiment, the present invention is not limited solely tothis particular embodiment; making various modifications to the aboveillustrated embodiment is possible.

For instance, the sector gear 211 that serves as the interlockingrotating member can be formed from two separate parts: a lever memberhaving an elongated hole in which the mirror drive shaft 400 is engaged,and a gear member which rotates integrally with the lever member inassociation with the brake drum 231. By forming the interlockingrotating member from two separate parts such as the lever member and thegear member, the degree of freedom in part shape and placementincreases.

Obvious changes may be made in the specific embodiment of the presentinvention described herein, such modifications being within the spiritand scope of the invention claimed. It is indicated that all mattercontained herein is illustrative and does not limit the scope of thepresent invention.

1. A mirror brake mechanism of an SLR camera for applying a brake to amirror pivoted about a mirror rotational shaft to be swingable between aviewing position, in which light traveling from a photographing opticalsystem is incident on said mirror and reflected toward a viewfinderoptical system, and a retracted position, in which the light travelingfrom said photographing optical system is incident on an image sensorwithout being reflected by said mirror, said mirror brake mechanismcomprising: a brake shaft which is independent of said mirror rotationalshaft and positionally aligned along an extension line of said mirrorrotational shaft; an interlocking rotating member disposed on one oflaterally opposite sides of said mirror and rotatable about said brakeshaft; a mirror drive shaft which connects a mirror seat, on which saidmirror is mounted, and said interlocking rotating member to each other,said mirror drive shaft configured to allow said mirror seat and saidinterlocking rotating member to rotate around an axis of said brakeshaft; a brake drum which rotates in association with said interlockingrotating member; and a mirror brake member which is brought into contactwith and disengaged from said brake drum.
 2. The mirror brake mechanismaccording to claim 1, wherein said interlocking rotating member, saidbrake drum and said mirror brake member are disposed on said one of saidlaterally opposite sides of said mirror.
 3. The mirror brake mechanismaccording to claim 1, wherein said interlocking rotating membercomprises an elongated hole elongated in a radial direction of saidinterlocking rotating member, and wherein said mirror drive shaft isconnected to a lateral side of said mirror seat and is inserted intosaid elongated hole of said interlocking rotating member.
 4. The mirrorbrake mechanism according to claim 3, wherein said interlocking rotatingmember comprises a sector gear, and wherein said mirror brake mechanismcomprises a speed-up gear train that is disposed between said sectorgear and said brake drum.
 5. The mirror brake mechanism according toclaim 1, wherein said mirror brake member comprises a brake lever thatis swingable between a brake applying position in which a brake shoefixed to one end of said brake lever is pressed against said brake drumto brake said brake drum and a brake release position in which saidbrake shoe is disengaged from said brake drum, and wherein said mirrorbrake mechanism further comprises a brake spring which biases said brakelever toward said brake applying position.
 6. The mirror brake mechanismaccording to claim 1, further comprising a mirror drive unit whichswings said mirror via said mirror drive shaft.
 7. The mirror brakemechanism according to claim 6, wherein said mirror drive unit comprisesan operatively associated mechanism which operates in association withsaid mirror drive unit to prevent said mirror brake member from applyinga brake to said brake drum when said mirror is in said viewing position,to brake said brake drum before said mirror reaches said retractedposition when said mirror swings from said viewing position to saidretracted position, and to release said brake from said brake drumapplied via said mirror brake member before said mirror commences toswing when said mirror swings from said retracted position to saidviewing position.
 8. The mirror brake mechanism according to claim 1,wherein axes of said brake shaft, said mirror drive shaft and said brakedrum are parallel to one another.
 9. The mirror brake mechanismaccording to claim 1, wherein said axis of said brake shaft is alignedwith an axis of said mirror rotational shaft.
 10. The mirror brakemechanism according to claim 1, wherein an axis of said mirror driveshaft is parallel to and not coaxially aligned with said axis of saidbrake shaft.
 11. The mirror brake mechanism according to claim 1,wherein said brake shaft, a gear train engaged with said interlockingrotating member, said brake drum, and said mirror brake member aremounted to a brake mount plate.